If you update your select as follows it will display by default to the users division.id.

<select ng-model="user.division" ng-options="d as d.name for d in divisions track by d.id">

You seemed to be wanting to have a separate model division_id, the only reason I can think of for this is that you wanted to control the persistence of the user model when the selection is updated. If for some reason you want to intercept the end-users selection to the user model (or even just the in-memory user object) being updated then use a copy/there are many ways to do that, but it's not clear if that's what you're asking.